<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
</head>
<body>
<script>
    var cc;
    function cc(){
        console.log('我是一个cc函数')
    }
    var b;
    function fun(){
        console.log('我是一个函数');
    }
    var a = 19;
    console.log(a);
    a = 20;
    console.log(a);

    console.log(b);

    fun();

    cc();



</script>
</body>
</html>